Our objectives is to establish a colony of highly asthmatic dogs to act as experimental models to study the pathophysiology of allergic reactions, and to develop new therapeutic methods. Our pervious screening of dogs revealed that about 5% were allergic to grass pollens. We plan to screen by allergy skin tests and symptoms to locate allergic animals. These will be bred. We have now bred 14 pairs of allergic dogs; this has resulted in 47 dogs that are making high titers of IgE antibodies to grass and ragweed pollens. Dogs are exposed to pollen antigens as puppies shortly after their immunization with live attenuated distemper virus vaccine. Two litters of puppies have been exposed to pollen aerosols and are making IgE antibodies. A canine moded of asthma has important applications to the study of allergic diseases in man, such as asthma. If we find consistently that virus infection precedes allergic sensitization in our puppies, it may then be possible to prevent such sensitization by prior immunization against certain viruses or by pharmacological means.